100TH MOLAR CALCIUM-CHLORIDE EXTRACTION PROCEDURE - PART I - A REVIEWOF SOIL CHEMICAL, ANALYTICAL, AND PLANT NUTRITIONAL ASPECTS

The economical and operational aspects of multinutrient extractants ma ke them attractive for soil testing programs. However, the value of a multi element extractant is primarily determined by the relationship b etween the amount of nutrient extracted and crop response. To determin e the perspectives of the 0.01M calcium chloride (CaCl2) extraction pr ocedure as a multinutrient extractant, this paper reviews literature o n the soil chemical, analytical and plant nutritional aspects of CaCl2 solutions as a soil extractant. Recent decades, CaCl2 solutions were common single nutrient extractants in plant nutritional and soil chemi cal research but the amount of nutrient extracted was sensitive for di fferences in sample treatment and extraction procedure. Therefore, a 0 .01M CaCl2 procedure should be standarized to obtain a robust procedur e. Calibration studies between conventional soil extraction procedure and the 0.01M CaCl2 procedure show fairly good relationships. A first step to develop a multielement 0.01M CaCl2 soil testing program is to convert conventional soil testing programs into 0.01M CaCl2 programs b ased on these relationships. Validation of these programs with pot and field experiments remains necessary. Further research is suggested to test if the 'labile' pool of plant nutrients in a soil can be estimat ed based on the pH. The composition of the supernatant and soil charac teristics. It is concluded that the 0.01M CaCl2 procedure is a promisi ng tool in near future farm nutrient management.